I had a recent communication through the American Society for Clinical Laboratory Science Consumer Forum in which a patient with severe chronic bleeding symptoms had been diagnosed as having both a factor VIII and a factor XIII deficiency. Given prevalence data, I compute the odds of this combination as 1 in 10 billion, and have found no published cases, though I found two cases of combined von Willebrand disease and factor XIII deficiency. I suggested the factor XIII deficiency conclusion could be false, based on a false positive urea solubility assay. It struck me that factor VIII deficiency would generate a weak clot that would dissolve in the urea solution, giving the false impression of a factor XIII deficiency, but I can’t find anything in writing to support my conclusion. I recommended the patient’s physician ensure the lab was using one of the updated chromogenic factor XIII assays. Do you have any experience with a combined VIII and XIII deficiency? Also, would you please comment on the urea solubility test?
I am trying to work on a hemostasis project for school and I do not have any experience at all in a hemostasis laboratory apart from running PT and PTTs. What if a patient has an abnormal PT and PTT that are not corrected by mixing study? My guess is because it didn’t correct, it would be an inhibitor. What are possible causes for these results? Carrie
From Robert Gosselin at UC-Davis in Sacramento:
Just as a side note, in the lupus anticoagulant comment you indicated “…which is performed using PFP, plasma whose platelet count is less than 10,000/mcL.” One has to assume that the abbreviation PFP is for platelet-free plasma as opposed to platelet-poor plasma. The former, platelet free plasma, is actually as it means, and usually requires filtration. Kaolin clotting time requires platelet free plasma for testing. However lupus anticoagulant testing using DRVVT requires platelet poor plasma, which is defined as being less than 10,000/mcL, and there is ample evidence to suggest that filtration is not recommended for non-KCT testing.
Robert Gosselin, CLS
University of California, Davis Health System
Department of Pathology and Laboratory Medicine
Specialty Testing Center
From Joe Lamb, St Francis Hospital, Columbus, GA:
I like all the recent questions about mixing studies. I’m trying to set up mixing studies in my lab. There are some procedures I have seen that suggest testing a sample of patient plasma and PNP after incubation to ensure the labile factors haven’t deteriorated during incubation. The saline mix is another wrinkle I’ve seen. My question, do you report these “extra” results? Does it confuse the clinician? I’d love to see a mixing study report or a list of exactly what you report. I don’t want to make the report too confusing or too long. Can you help me?
Joe Lamb, MT (ASCP)
Hematology/Blood Bank Supervisor